Create alert in Grafana - based on delta between 2 time series

Question

I have 2 timeseries (A and B) implemented in InfluxDB and visualized in Grafana. I would like to calculate the delta D = A - B, for each time-point. If D>X (x = value threshold), it needs to create an alert I Grafana. My question is, how best to do this?

Answer 1

I just encountered the same need. I created a synthetic variable with metric #F and diffSeries(#H) where F and H are the raw data series. I also did a removeAbovePercentile(80) so that sampling misalignment don't spike the series. My data is stored in graphite/whisper; you should be able to do something similar w/ influxDb.